Radicals are an important class of versatile and highly reactive http://www.doczj.com/doc/29f57db0f01dc281e43af00b.html pared with the wide applications of various C-centred radicals,however,the N-radical species including N-centred radicals and radical ions remain largely unexplored due to the lack of convenient methods for their generation.

In recent years,visible light photoredox catalysis has emerged as a powerful platform for the generation of various N-radical species and methodology development towards the synthesis of diverse N-containing compounds.In this tutorial review,we highlight recent advances in this rapidly developing area with particular emphases put on the working models and new reaction design.

Introduction

Free radical reactions represent a powerful class of chemical transformations and have attracted considerable attention from the synthetic community because of their high eﬃciency and unique reactivity.1,2In particular,significant progresses have been made in the chemistry of carbon radicals over the past several http://www.doczj.com/doc/29f57db0f01dc281e43af00b.html pared with the popularity of carbon-centred radicals,however,the synthetic utilities of N-centred radical species,including N-radicals and N-radical ions remain relatively unexplored due to the lack of general and convenient methods for their generation.The N-radical species are historically generated by stoichiometric radical initiators,thermolysis or photolysis.3However,the requirement for some hazardous radical initiators,elevated temperature,or high-energy UV irradiation largely limits their broad applications in modern synthetic chemistry.

Over recent years,visible light photocatalysis,4using visible light as a renewable energy source,has been established as a powerful and mild technique to facilitate activation of organic

molecules and engineer new chemical processes selectively since the seminal studies from the groups of MacMillan,5Yoon,6and Stephenson.7In this context,such a catalytic strategy has also proven to be a mild and general tool for the conversion of N-containing compounds into highly reactive N-radical species in a controlled way,thus enabling achievement of a wide variety of new chemical reactions towards the synthesis of diversely functionalized N-containing molecules.Elegant examples from the most recent literature also demonstrate the significance of this fast developing area of research.To the best of our knowledge,however,there is still no review devoted to this emerging topic so far.Therefore,a tutorial review highlighting the main advances in this area should be timely and desirable,and will attract more research interests to this field.Therefore,we will highlight the recent advances on visible light photoredox-controlled reactions of N-radical species with particular emphases put on the working models.To calibrate the reasonable scope of this survey,this review is mainly organized based on diﬀerent types of N-radical species and their precursors.

1.Neutral N-centred radicals

The C–N bonds are prominent functionalities in organic mole-cules and it is reported that about 84%of small-molecule pharmaceuticals contain at least one C–N bond.8The